Terpendole e and its derivative inhibit STLC- and GSK-1-resistant Eg5

Abstract

Terpendole E is first natural product found to inhibit mitotic kinesin Eg5, but its inhibitory mechanism remains to be revealed. Here, we report the effects of terpendole E and 11ketopaspaline (a new natural terpendole E analogue) on the Eg5-microtubule interaction and in several Eg5 mutants. 11-Ketopaspaline is a shunt product from terpendole E, and it shows potent inhibitory activity against the microtubule-stimulated ATPase activity of Eg5. Unlike other Eg5 inhibitors, such as S-trityl-L-cysteine (STLC) and GSK-1, both terpendole E and 11-ketopaspaline only partially inhibited Eg5-microtubule interaction. Furthermore, terpendole E and 11-ketopaspaline inhibited several Eg5 mutants that are resistant to STLC (Eg5D130A, Eg5 L214A) or GSK-1 (Eg5I299F, Eg5A356T), but with the same extent of inhibition against wild-type Eg5. Because Eg5D130A and Eg5L214A show cross-resistance to most known Eg5 inhibitors, which bind the L5 loop, these results suggest that terpendole E and its analogues have a different binding site and/or inhibitory mechanism to those for L5 loop-binding type Eg5 inhibitors. Out of the loop? A new natural Eg5 inhibitor, 11-ketopaspaline, was isolated, and the effects of terpendole E and 11-ketopaspaline on Eg5-microtubule interaction in several Eg5 mutants were investigated. Terpendole E and its analogues might have a binding site and/or inhibitory mechanism than differ from those of L5 loop-binding-type Eg5 inhibitors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.